python 实现链表

以下是Python实现单链表的示例代码：

# 定义链表节点类
class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

# 定义链表类
class LinkedList:
    def __init__(self):
        self.head = None

    # 在链表末尾添加节点
    def addAtTail(self, val: int) -> None:
        if not self.head:
            self.head = ListNode(val)
        else:
            cur = self.head
            while cur.next:
                cur = cur.next
            cur.next = ListNode(val)

    # 在链表头部添加节点
    def addAtHead(self, val: int) -> None:
        if not self.head:
            self.head = ListNode(val)
        else:
            new_head = ListNode(val)
            new_head.next = self.head
            self.head = new_head

    # 在指定位置添加节点
    def addAtIndex(self, index: int, val: int) -> None:
        if index == 0:
            self.addAtHead(val)
        else:
            cur = self.head
            for i in range(index - 1):
                if not cur:
                    return
                cur = cur.next
            if not cur:
                return
            new_node = ListNode(val)
            new_node.next = cur.next
            cur.next = new_node

    # 删除指定位置的节点
    def deleteAtIndex(self, index: int) -> None:
        if not self.head:
            return
        if index == 0:
            self.head = self.head.next
        else:
            cur = self.head
            for i in range(index - 1):
                if not cur:
                    return
                cur = cur.next
            if not cur or not cur.next:
                return
            cur.next = cur.next.next

    # 获取指定位置的节点值
    def get(self, index: int) -> int:
        if not self.head:
            return -1
        cur = self.head
        for i in range(index):
            if not cur:
                return -1
            cur = cur.next
        if not cur:
            return -1
        return cur.val

    # 打印链表
    def printList(self) -> None:
        if not self.head:
            print("Empty List")
        else:
            cur = self.head
            while cur:
                print(cur.val, end=" ")
                cur = cur.next
            print()

# 创建链表并测试
linked_list = LinkedList()
linked_list.addAtHead(1)
linked_list.addAtTail(3)
linked_list.addAtIndex(1, 2)
linked_list.printList() # 输出：1 2 3
linked_list.deleteAtIndex(1)
linked_list.printList() # 输出：1 3
print(linked_list.get(1)) # 输出：3